The Dysregulated Galectin Network Activates NF-κB to Induce Disease Markers and Matrix Degeneration in 3D Pellet Cultures of Osteoarthritic Chondrocytes

Targeting osteoarthritis-associated galectins and an induced effector class by a ditopic bifunctional reagent: Impact of its glycan part on binding measured in the tissue context

Pairing glycans with tissue lectins controls multiple effector pathways in (patho)physiology. A clinically relevant example is the prodegradative activity of galectins-1 and -3 (Gal-1 and -3) in the progression of osteoarthritis (OA) via matrix metalloproteinases (MMPs), especially MMP-13. The design of heterobifunctional inhibitors that can block galectin binding and MMPs both directly and by preventing their galectin-dependent induction selectively offers a perspective to dissect the roles of lectins and proteolytic enzymes. We describe the synthesis of such a reagent with a bivalent galectin ligand connected to an MMP inhibitor and of two tetravalent glycoclusters with a subtle change in headgroup presentation for further elucidation of influence on ligand binding. Testing was performed on clinical material with mixtures of galectins as occurring in vivo, using sections of fixed tissue. Two-colour fluorescence microscopy monitored binding to the cellular glycome after optimization of experimental parameters. In the presence of the inhibitor, galectin binding to OA specimens was significantly reduced. These results open the perspective to examine the inhibitory capacity of custom-made ditopic compounds on binding of lectins in mixtures using sections of clinical material with known impact of galectins and MMPs on disease progression.

A Progress Report and Roadmap for Microphysiological Systems and Organ-On-A-Chip Technologies to Be More Predictive Models in Human (Knee) Osteoarthritis

Osteoarthritis (OA), a chronic debilitating joint disease affecting hundreds of million people globally, is associated with significant pain and socioeconomic costs. Current treatment modalities are palliative and unable to stop the progressive degeneration of articular cartilage in OA. Scientific attention has shifted from the historical view of OA as a wear-and-tear cartilage disorder to its recognition as a whole-joint disease, highlighting the contribution of other knee joint tissues in OA pathogenesis. Despite much progress in the field of microfluidic systems/organs-on-a-chip in other research fields, current in vitro models in use do not yet accurately reflect the complexity of the OA pathophenotype. In this review, we provide: 1) a detailed overview of the most significant recent developments in the field of microsystems approaches for OA modeling, and 2) an OA-pathophysiology-based bioengineering roadmap for the requirements of the next generation of more predictive and authentic microscale systems fit for the purpose of not only disease modeling but also of drug screening to potentially allow OA animal model reduction and replacement in the near future.

Anti-Inflammatory and Pro-Regenerative Effects of Hyaluronan-Chitlac Mixture in Human Dermal Fibroblasts: A Skin Ageing Perspective

Inflammation and the accumulation of reactive oxygen species (ROS) play an important role in the structural and functional modifications leading to skin ageing. The reduction of inflammation, cellular oxidation and dermal extracellular matrix (ECM) alterations may prevent the ageing process. The aim of this study is to investigate the expression of pro-inflammatory markers and ECM molecules in human dermal fibroblasts derived from young and middle-aged women and the effects of lactose-modified chitosan (Chitlac®, CTL), alone or in combination with mid-MW hyaluronan (HA), using an in vitro model of inflammation. To assess the response of macrophage-induced inflamed dermal fibroblasts to HA and CTL, changes in cell viability, pro-inflammatory mediators, MMPs and ECM molecules expression and intracellular ROS generation are analysed at gene and protein levels. The expression of pro-inflammatory markers, galectins, MMP-3 and ECM molecules is age-related. CTL, HA and their combination counteracted the oxidative damage, stimulating the expression of ECM molecules, and, when added to inflamed cells, restored the baseline levels of IL-1β, TNF-α, GAL-1, GAL-3 and MMP-3. In conclusion, HA and CTL mixture attenuated the macrophage-induced inflammation, inhibited the MMP-3 expression, exhibited the anti-oxidative effects and exerted a pro-regenerative effect on ECM.

Galectin network in osteoarthritis: galectin-4 programs a pathogenic signature of gene and effector expression in human chondrocytes in vitro

Galectin-4 (Gal-4) is a member of the galectin family, which have been identified as galactose-binding proteins. Gal-4 possesses two tandem repeat carbohydrate recognition domains and acts as a cross-linking bridge in sulfatide-dependent glycoprotein routing. We herein document its upregulation in osteoarthritis (OA) in correlation with the extent of cartilage degradation in vivo. Primary human OA chondrocytes in vitro respond to carbohydrate-inhibitable Gal-4 binding with the upregulation of pro-degradative/-inflammatory proteins such as interleukin-1β (IL-1β) and matrix metalloproteinase-13 (MMP-13), as documented by RT-qPCR-based mRNA profiling and transcriptome data processing. Activation of p65 by phosphorylation of Ser536 within the NF-κB pathway and the effect of three p65 inhibitors on Gal-4 activity support downstream involvement of such signaling. In 3D (pellet) cultures, Gal-4 presence causes morphological and biochemical signs of degradation. Taken together, our findings strongly support the concept of galectins acting as a network in OA pathogenesis and suggest that blocking their activity in disease progression may become clinically relevant in the future.

What is the Sugar Code?

A code is defined by the nature of the symbols, which are used to generate information‐storing combinations (e. g. oligo‐ and polymers). Like nucleic acids and proteins, oligo‐ and polysaccharides are ubiquitous, and they are a biochemical platform for establishing molecular messages. Of note, the letters of the sugar code system (third alphabet of life) excel in coding capacity by making an unsurpassed versatility for isomer (code word) formation possible by variability in anomery and linkage position of the glycosidic bond, ring size and branching. The enzymatic machinery for glycan biosynthesis (writers) realizes this enormous potential for building a large vocabulary. It includes possibilities for dynamic editing/erasing as known from nucleic acids and proteins. Matching the glycome diversity, a large panel of sugar receptors (lectins) has developed based on more than a dozen folds. Lectins ‘read’ the glycan‐encoded information. Hydrogen/coordination bonding and ionic pairing together with stacking and C−H/π‐interactions as well as modes of spatial glycan presentation underlie the selectivity and specificity of glycan‐lectin recognition. Modular design of lectins together with glycan display and the nature of the cognate glycoconjugate account for the large number of post‐binding events. They give an entry to the glycan vocabulary its functional, often context‐dependent meaning(s), hereby building the dictionary of the sugar code.